Display screen or portion thereof with a graphical user interface



FIG. 1 is front view of a display screen or portion thereof with a graphical user interface showing an embodiment of our new design;

FIG. 2 is a front view of a display screen or portion thereof with a graphical user interface showing another embodiment of our new design;

FIG. 3 is a front view of a display screen or portion thereof with a graphical user interface showing another embodiment of our new design;

FIG. 4 is a front view of a display screen or portion thereof with a graphical user interface showing another embodiment of our new design;

FIG. 5 is a front view of a display screen or portion thereof with a graphical user interface showing another embodiment of our new design; and,

FIG. 6 is a front view of a display screen or portion thereof with a graphical user interface showing another embodiment of our new design.

The broken lines showing a display screen or portion thereof illustrate portions of the article, and form no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with a graphical user interface, as shown and described. 